Short-run production is increasingly utilized in today's competitive manufacturing environments. In order to meet such demands, many dedicated assembly lines are being replaced with flexible systems which enable rapid changeover of the line, thereby increasing the efficiency of production. Unfortunately, the industrial workcells, which typically employ programmable robots, have become extremely complex and the difficulty in modifying the operations of such workcells has resulted in rather inflexible assembly lines.
Flexible assembly is the ability of an automated or robot system to assemble different parts into different assembled units. For example, at the beginning of the workday a robot may be configured to place and secure circuit boards into the chassis of personal computers. After completing a desired quantity of assemblies the robot may be instructed to assemble components for a paper path in a xerographic copier. Although the materials and tools are different, the work processes share similarities that can be modeled such that a unified architecture can be developed to satisfy all types of flexible robot assembly applications.
The present invention is directed toward alleviating one of three types of data flow and control problems which arise within such a flexible assembly system, including: 1) encoding the location of workpieces used by robots in the workcell; 2) collecting and processing error data during production; and 3) providing flexibility in the control of operations within the system.
The first problem is resolved using a method and apparatus for defining the position of workpieces held on pallets used within a flexible assembly system. The pallet configuration capability of the present invention captures the geometrical configuration of workpieces on any type of pallet (i.e., a universal pallet) and translates the configuration into a data record which the robot understands.
The second problem is alleviated using a method which encodes process error data transmitted between the components of the flexible assembly system. This encoded or "encapsulated" error data, is subsequently used to identify substandard workpieces to a particular position on the pallet. The use of the encapsulated error data further enables efficient pallet routing decisions to be executed within the FAS cell. Ultimately, the proposed system improves the quality of the end items or assemblies produced therein.
The last problem in the flexible assembly system is resolved using a method which provides the user the choice of running a workcell either locally (at one of the robot stations), or at a remote source (a remotely located computer). Control capability from a remote system, a cell controller, is incorporated into the architecture, because of the advantages remote control provides. Remote control of cell operations correctly implies that multiple workcells containing multiple robots can be effectively controlled from a single location on the production floor. This in turn implies that fewer operators would be required to oversee a greater number of production operations, thereby further improving productivity.
The use of robots for the assembly of workpieces arranged in predefined locations is known, and control of the robots by a microcontroller which executes commands entered via a proprietary software language is also known. For example, Adept robots (Adept Technology, Incorporated, San Jose, Calif.) utilize the V+language to create Pascal-like data records to define system characteristics. Robotic systems have commonly been employed in "dedicated" or highly repetitive operations that remain constant over long runs on an assembly line. As a result, the need for flexibility in the system, including the ease of modifying the robot operations or other system characteristics, was not a priority in such systems. Hence, alteration of the operation of the systems usually requires knowledge of the proprietary robot language and system characteristics in order to effect the desired changes or, in other words, a person having a high level of technical training is needed to effect alterations in the robot's process.
Heretofore, many such "dedicated" assembly systems have been developed to fabricate and inspect mechanical and electrical assemblies, of which the following disclosures may be relevant: